You mix UI and UX polish, and the UX on OpenOffice is honestly not very good ... I only had to use it the other day and struggled with finding half a dozen things that are just obvious with Word.
For complete novices, yes the UI is not very intuitive. But Word isn’t much better either.
I recently had to start using Word again at work and even though the ribbons seem intuitive and user-friendly, actually finding the feature I needed has not always been easy. I’ve had to Google quite a bit (the help is excellent though).
At least in LibreOffice everything is always in the menus and does not suddenly disappear if your window is not wide enough.
UX doesn't enter into my criticism here.